/* =========================================================================
   Homepage Tab — Landing Page Stylesheet
   设计原则：
   - 暗色优先（@media prefers-color-scheme 自动切换）
   - 字体栈使用系统字体（零依赖、零字体抖动）
   - 设计令牌集中管理（CSS 变量）
   - 移动端优先 + 桌面端断点
   - 无外部库，可被任何静态托管直接服务
   ========================================================================= */

/* -------------------- 设计令牌（亮色与暗色） -------------------- */

:root {
  /* 留白节奏 */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 24px;
  --space-6: 32px;
  --space-7: 48px;
  --space-8: 64px;
  --space-9: 96px;
  --space-10: 128px;

  /* 圆角 */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-pill: 9999px;

  /* 字体 */
  --font-system: -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue",
    "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;

  /* 容器宽度 */
  --container-max: 1200px;
  --container-narrow-max: 720px;

  /* 阴影 */
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 24px 64px rgba(15, 23, 42, 0.12);

  /* 缓动 */
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
}

/* 亮色主题 */
:root,
:root[data-theme="light"] {
  color-scheme: light;
  --bg: #ffffff;
  --bg-elevated: #ffffff;
  --bg-subtle: #f6f7f9;
  --bg-overlay: rgba(255, 255, 255, 0.72);
  --border: rgba(15, 23, 42, 0.08);
  --border-strong: rgba(15, 23, 42, 0.14);
  --fg: #0b0d12;
  --fg-strong: #060810;
  --fg-muted: #5b6473;
  --fg-subtle: #8a909e;
  --accent: #4f46e5;
  --accent-hover: #4338ca;
  --accent-soft: rgba(79, 70, 229, 0.08);
  --accent-fg: #ffffff;
  --grad-start: #6366f1;
  --grad-mid: #8b5cf6;
  --grad-end: #ec4899;
  --hero-bg: radial-gradient(
      circle at 20% 0%,
      rgba(99, 102, 241, 0.18),
      transparent 60%
    ),
    radial-gradient(circle at 80% 0%, rgba(236, 72, 153, 0.14), transparent 55%),
    linear-gradient(180deg, #ffffff 0%, #f8fafc 100%);
}

/* 暗色主题 */
@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;
    --bg: #0b0d12;
    --bg-elevated: #11141b;
    --bg-subtle: #161a23;
    --bg-overlay: rgba(11, 13, 18, 0.72);
    --border: rgba(255, 255, 255, 0.08);
    --border-strong: rgba(255, 255, 255, 0.16);
    --fg: #e7e9ee;
    --fg-strong: #ffffff;
    --fg-muted: #a3a8b3;
    --fg-subtle: #6b7280;
    --accent: #818cf8;
    --accent-hover: #a5b4fc;
    --accent-soft: rgba(129, 140, 248, 0.12);
    --accent-fg: #0b0d12;
    --grad-start: #818cf8;
    --grad-mid: #a78bfa;
    --grad-end: #f472b6;
    --hero-bg: radial-gradient(
        circle at 20% 0%,
        rgba(99, 102, 241, 0.22),
        transparent 60%
      ),
      radial-gradient(
        circle at 80% 0%,
        rgba(236, 72, 153, 0.16),
        transparent 55%
      ),
      linear-gradient(180deg, #0b0d12 0%, #0a0c11 100%);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.32);
    --shadow-lg: 0 24px 64px rgba(0, 0, 0, 0.42);
  }
}

/* 用户手动切换 */
:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0b0d12;
  --bg-elevated: #11141b;
  --bg-subtle: #161a23;
  --bg-overlay: rgba(11, 13, 18, 0.72);
  --border: rgba(255, 255, 255, 0.08);
  --border-strong: rgba(255, 255, 255, 0.16);
  --fg: #e7e9ee;
  --fg-strong: #ffffff;
  --fg-muted: #a3a8b3;
  --fg-subtle: #6b7280;
  --accent: #818cf8;
  --accent-hover: #a5b4fc;
  --accent-soft: rgba(129, 140, 248, 0.12);
  --accent-fg: #0b0d12;
  --grad-start: #818cf8;
  --grad-mid: #a78bfa;
  --grad-end: #f472b6;
  --hero-bg: radial-gradient(
      circle at 20% 0%,
      rgba(99, 102, 241, 0.22),
      transparent 60%
    ),
    radial-gradient(circle at 80% 0%, rgba(236, 72, 153, 0.16), transparent 55%),
    linear-gradient(180deg, #0b0d12 0%, #0a0c11 100%);
}

/* -------------------- 重置 -------------------- */

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  font-family: var(--font-system);
  font-size: 16px;
  line-height: 1.6;
  color: var(--fg);
  background: var(--bg);
  -webkit-tap-highlight-color: transparent;
}

img,
svg {
  display: block;
  max-width: 100%;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.18s var(--ease-out);
}
a:hover {
  color: var(--accent-hover);
}
a:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 2px;
}

h1,
h2,
h3,
h4 {
  margin: 0;
  color: var(--fg-strong);
  letter-spacing: -0.02em;
  line-height: 1.2;
}

p {
  margin: 0;
}

ul {
  margin: 0;
  padding: 0;
  list-style: none;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: 0;
  background: none;
  color: inherit;
  padding: 0;
}

/* -------------------- 跳过链接（a11y） -------------------- */

.skip-link {
  position: absolute;
  top: -100px;
  left: var(--space-4);
  padding: var(--space-2) var(--space-4);
  background: var(--fg-strong);
  color: var(--bg);
  border-radius: var(--radius-sm);
  z-index: 1000;
  transition: top 0.18s var(--ease-out);
}
.skip-link:focus {
  top: var(--space-4);
}

/* -------------------- 容器 -------------------- */

.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-5);
}

@media (min-width: 768px) {
  .container {
    padding: 0 var(--space-6);
  }
}

.container-narrow {
  max-width: var(--container-narrow-max);
}

/* -------------------- Header / Nav -------------------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: saturate(140%) blur(12px);
  -webkit-backdrop-filter: saturate(140%) blur(12px);
  background: var(--bg-overlay);
  border-bottom: 1px solid transparent;
  transition: border-color 0.18s var(--ease-out);
}
.site-header[data-elevate].is-elevated {
  border-bottom-color: var(--border);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-5);
  height: 64px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--fg-strong);
  font-weight: 600;
  font-size: 17px;
  letter-spacing: -0.01em;
}
.brand:hover {
  color: var(--fg-strong);
}
.brand-logo {
  width: 32px;
  height: 32px;
  border-radius: 8px;
}

.primary-nav {
  display: flex;
  align-items: center;
  gap: var(--space-5);
}
.primary-nav a {
  font-size: 14px;
  font-weight: 500;
  color: var(--fg-muted);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
}
.primary-nav a:hover {
  color: var(--fg-strong);
  background: var(--accent-soft);
}
.primary-nav .nav-cta {
  background: var(--fg-strong);
  color: var(--bg);
  padding: var(--space-2) var(--space-5);
  font-weight: 600;
}
.primary-nav .nav-cta:hover {
  background: var(--accent);
  color: var(--accent-fg);
}

@media (max-width: 600px) {
  .primary-nav a:not(.nav-cta) {
    display: none;
  }
}

/* -------------------- 段落标识 / Eyebrow -------------------- */

.eyebrow {
  display: inline-block;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: 12px;
  font-weight: 600;
  color: var(--accent);
  margin: 0 0 var(--space-4) 0;
}

.eyebrow-pulse::before {
  content: "";
  display: inline-block;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--accent);
  margin-right: var(--space-2);
  vertical-align: 1px;
  animation: pulse 2s var(--ease-in-out) infinite;
}

@keyframes pulse {
  0%,
  100% {
    transform: scale(1);
    opacity: 1;
  }
  50% {
    transform: scale(1.4);
    opacity: 0.5;
  }
}

/* -------------------- Hero -------------------- */

.hero {
  position: relative;
  padding: var(--space-9) 0 var(--space-7);
  background: var(--hero-bg);
  overflow: hidden;
  text-align: center;
}

.hero-inner {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.hero-title {
  font-size: clamp(40px, 7vw, 80px);
  font-weight: 700;
  letter-spacing: -0.035em;
  line-height: 1.05;
  margin: 0 0 var(--space-5) 0;
  max-width: 18ch;
}

.hero-title-leading {
  display: block;
  color: var(--fg-strong);
}

.hero-title-accent {
  display: block;
  background: linear-gradient(
    100deg,
    var(--grad-start) 0%,
    var(--grad-mid) 50%,
    var(--grad-end) 100%
  );
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero-subtitle {
  font-size: clamp(17px, 2vw, 21px);
  color: var(--fg-muted);
  max-width: 56ch;
  margin: 0 auto var(--space-7) auto;
}

.hero-ctas {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
}

.hero-meta {
  font-size: 13px;
  color: var(--fg-subtle);
  margin-top: var(--space-3);
}

.hero-screenshot {
  margin: var(--space-9) 0 0 0;
  width: 100%;
  max-width: 1100px;
}

.hero-screenshot-frame {
  border-radius: var(--radius-xl);
  overflow: hidden;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-lg);
  position: relative;
  transition: transform 0.4s var(--ease-out), box-shadow 0.4s var(--ease-out);
}

.hero-screenshot-frame:hover {
  transform: translateY(-4px);
}

.hero-screenshot img {
  width: 100%;
  height: auto;
  display: block;
}

/* -------------------- Buttons -------------------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: 14px 24px;
  border-radius: var(--radius-pill);
  font-size: 15px;
  font-weight: 600;
  letter-spacing: -0.005em;
  transition: transform 0.18s var(--ease-out),
    background 0.18s var(--ease-out), box-shadow 0.18s var(--ease-out);
  white-space: nowrap;
  user-select: none;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary {
  background: var(--fg-strong);
  color: var(--bg);
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
  background: var(--accent);
  color: var(--accent-fg);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: var(--bg-subtle);
  color: var(--fg-strong);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--bg-elevated);
  color: var(--fg-strong);
  border-color: var(--border-strong);
}

.btn-icon {
  width: 16px;
  height: 16px;
  flex-shrink: 0;
}

/* -------------------- Section 通用 -------------------- */

.section {
  padding: var(--space-9) 0;
}

@media (min-width: 768px) {
  .section {
    padding: var(--space-10) 0;
  }
}

.section-head {
  text-align: center;
  max-width: 720px;
  margin: 0 auto var(--space-8) auto;
}

.section-title {
  font-size: clamp(30px, 4.2vw, 48px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin: 0 0 var(--space-4) 0;
}

.section-subtitle {
  font-size: clamp(16px, 1.8vw, 19px);
  color: var(--fg-muted);
  margin: 0;
}

/* -------------------- Features -------------------- */

.feature-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-4);
}

@media (min-width: 600px) {
  .feature-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-5);
  }
}

@media (min-width: 1000px) {
  .feature-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.feature-card {
  padding: var(--space-6);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-elevated);
  transition: transform 0.3s var(--ease-out), border-color 0.3s var(--ease-out);
}

.feature-card:hover {
  transform: translateY(-2px);
  border-color: var(--border-strong);
}

.feature-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  font-size: 28px;
  background: var(--accent-soft);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-4);
}

.feature-title {
  font-size: 18px;
  font-weight: 600;
  margin: 0 0 var(--space-2) 0;
}

.feature-desc {
  color: var(--fg-muted);
  font-size: 15px;
  line-height: 1.55;
}

/* -------------------- Screenshots -------------------- */

.screenshots {
  background: var(--bg-subtle);
}

.screenshot-row {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-5);
}

@media (min-width: 768px) {
  .screenshot-row {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-6);
  }
}

.screenshot-card {
  margin: 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  transition: transform 0.3s var(--ease-out), box-shadow 0.3s var(--ease-out);
}

.screenshot-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.screenshot-card img {
  width: 100%;
  height: auto;
  display: block;
  aspect-ratio: 16 / 10;
  object-fit: cover;
}

.screenshot-card figcaption {
  padding: var(--space-4) var(--space-5);
  font-size: 14px;
  color: var(--fg-muted);
  border-top: 1px solid var(--border);
}

/* -------------------- Why us -------------------- */

.why-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-5);
}

@media (min-width: 600px) {
  .why-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1000px) {
  .why-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

.why-card {
  padding: var(--space-6);
  text-align: left;
}

.why-icon {
  display: inline-flex;
  font-size: 36px;
  margin-bottom: var(--space-4);
}

.why-card h3 {
  font-size: 17px;
  font-weight: 600;
  margin: 0 0 var(--space-2) 0;
}

.why-card p {
  color: var(--fg-muted);
  font-size: 15px;
}

/* -------------------- Final CTA -------------------- */

.cta {
  background: var(--hero-bg);
  text-align: center;
}

.cta-inner {
  max-width: 720px;
}

.cta-title {
  font-size: clamp(28px, 4.5vw, 48px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.15;
  margin: 0 0 var(--space-4) 0;
}

.cta-subtitle {
  font-size: clamp(16px, 1.8vw, 19px);
  color: var(--fg-muted);
  margin: 0 0 var(--space-7) 0;
}

.cta-buttons {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-3);
}

/* -------------------- Footer -------------------- */

.site-footer {
  border-top: 1px solid var(--border);
  background: var(--bg-subtle);
  padding-top: var(--space-9);
}

.footer-inner {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-7);
}

@media (min-width: 800px) {
  .footer-inner {
    grid-template-columns: 1fr 2fr;
  }
}

.footer-brand .brand-text {
  font-size: 18px;
  font-weight: 600;
}

.footer-tagline {
  margin-top: var(--space-3);
  color: var(--fg-muted);
  font-size: 14px;
  max-width: 28ch;
}

.footer-links {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-6);
}

@media (min-width: 600px) {
  .footer-links {
    grid-template-columns: repeat(4, 1fr);
  }
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.footer-col-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--fg-strong);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin: 0 0 var(--space-2) 0;
}

.footer-col a {
  font-size: 14px;
  color: var(--fg-muted);
}
.footer-col a:hover {
  color: var(--fg-strong);
}

.footer-col a[aria-current="true"] {
  color: var(--fg-strong);
  font-weight: 600;
}

/* 紧凑 footer（用于法律页） */
.footer-inner-compact {
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  text-align: center;
}
@media (min-width: 768px) {
  .footer-inner-compact {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    text-align: left;
  }
}
.footer-links-compact {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-5);
}
.footer-links-compact a {
  font-size: 14px;
  color: var(--fg-muted);
}
.footer-links-compact a:hover {
  color: var(--fg-strong);
}

.footer-bottom {
  margin-top: var(--space-7);
  padding: var(--space-5) 0;
  border-top: 1px solid var(--border);
  text-align: center;
  font-size: 13px;
  color: var(--fg-subtle);
}

.footer-bottom-inner {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  align-items: center;
}

.footer-bottom .footer-copyright,
.footer-bottom .footer-icp {
  margin: 0;
}

/* 无备案文案的语言：不占据空白行 */
.footer-bottom .footer-icp:empty {
  display: none;
}

.footer-icp a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 2px;
}

.footer-icp a:hover {
  color: var(--fg-muted);
}

/* -------------------- 法律页（隐私政策 / 服务条款） -------------------- */

.legal-page {
  padding: var(--space-8) 0 var(--space-9);
}

.legal-head {
  text-align: center;
  margin-bottom: var(--space-8);
}

.legal-title {
  font-size: clamp(32px, 5vw, 48px);
  font-weight: 700;
  letter-spacing: -0.025em;
  margin: 0 0 var(--space-3) 0;
}

.legal-updated {
  font-size: 14px;
  color: var(--fg-subtle);
  margin: 0;
}

.legal-body {
  font-size: 16px;
  line-height: 1.75;
  color: var(--fg);
}

.legal-body h2 {
  font-size: 24px;
  font-weight: 700;
  margin: var(--space-7) 0 var(--space-4) 0;
  letter-spacing: -0.015em;
}

.legal-body h3 {
  font-size: 19px;
  font-weight: 600;
  margin: var(--space-6) 0 var(--space-3) 0;
}

.legal-body h2:first-child,
.legal-body h3:first-child {
  margin-top: 0;
}

.legal-body p {
  margin: 0 0 var(--space-4) 0;
}

.legal-body strong {
  color: var(--fg-strong);
  font-weight: 600;
}

.legal-body code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  padding: 2px 6px;
  background: var(--bg-subtle);
  border-radius: 4px;
  border: 1px solid var(--border);
}

.legal-body ul {
  margin: 0 0 var(--space-4) 0;
  padding-left: var(--space-5);
  list-style: disc;
}

.legal-body li {
  margin-bottom: var(--space-2);
}

.legal-body a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 2px;
}

/* -------------------- 重定向页（根 index.html） -------------------- */

.redirect-page {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-7);
  background: var(--hero-bg);
}

.redirect-page h1 {
  font-size: clamp(24px, 4vw, 36px);
  font-weight: 700;
  margin: 0 0 var(--space-5) 0;
}

.redirect-page p {
  color: var(--fg-muted);
  margin: 0 0 var(--space-6) 0;
}

.redirect-langs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-3);
  justify-content: center;
}

.redirect-langs a {
  padding: var(--space-3) var(--space-5);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-pill);
  font-weight: 500;
  color: var(--fg-strong);
}

.redirect-langs a:hover {
  border-color: var(--accent);
  background: var(--accent-soft);
}

/* -------------------- 入场动画 -------------------- */

.fade-in-up {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.8s var(--ease-out), transform 0.8s var(--ease-out);
}

.fade-in-up.is-visible {
  opacity: 1;
  transform: translateY(0);
}